In automotive manufacturing, polymetric composites are being used increasingly due to their favorable characteristics, such as being lightweight, highly-conformable or shapeable, strong, and durable. Some composites are further colorable and can be finished to have most any desired texture.
The increased use in automobiles includes, for instance, in instrument and door panels, lamps, air ducts, steering wheels, upholstery, truck beds or other vehicle storage compartments, upholstery, external parts, and even engine components. Regarding engine components, and other under-the-hood (or, UTH) applications, for instance, polymers are configured, and being developed continuously, that can withstand a hot and/or chemically aggressive environment. Regarding external parts, such as fenders, polymers are being developed that are online paintability and have high heat and chemical resistance over longer periods of time. And many other potential usages in automotive applications are being considered continuously.
With the increased use of polymers and other low-mass materials, compression molding and post-mold joining techniques—e.g., ultrasonic welding —are also being used more commonly.
Because some materials being used increasingly, including polymer composites, have relatively low melting points, a challenge arises in efforts to melt the parts at an interface joining the parts quickly and with minimal melting of other portions of the workpieces.
Energy directors are sometimes used to expedite and control welding. Once challenge arising in using energy directors is that they require a relatively large amount of input energy to function properly.
More particularly, in order for input energy, such as high-frequency vibrations, in the case of ultrasonic welding, to pass effectively through conventional directors, the energy has to be high enough to reach the director, through the first workpiece, and further to overcome resistance also of the director, itself, at all places where the director will melt.
In addition to higher than desired energy requirement, conventional approaches also require an undesirably-high cycle time—i.e., the time required for the energy to negotiate the workpieces and director as needed to form the weld.
The increased time and energy requirements are cost prohibitive, especially when multiplied by repeated iterations processing in a manufacturing environment—e.g., automobile assembly plant.